Isoplanatism of ground-based optical systems with multiconjugate adaptive phase correction

Subject of study . The aspects of the accounting of the isoplanatism phenomenon in multiconjugate adaptive optical systems (AOSs) designed for observing objects in low Earth orbits were investigated. Aim of study . The aims were to obtain analytical expressions and calculate the isoplanatism angle of a ground-based optical system under multiconjugate adaptive correction of atmospheric phase distortions. Main results . For given conjugation heights of the wavefront correctors in a multiconjugate AOS, the value of the isoplanatism angle was determined by considering the distribution of residual errors of adaptive phase correction along the altitude of the optical radiation propagation path in the atmosphere. For a standard model of the vertical profile of the refractive index structure constant, the isoplanatism angles for two-conjugate and three-conjugate adaptive correction were calculated, and the maximum achievable increment in the isoplanatism angle with respect to that for single-conjugate adaptive correction was determined. The influence of the adaptive correction of atmospheric phase distortions in the middle atmospheric layers on the increase in the isoplanatism angle of a ground-based optical system was evaluated through geometric representation analyses. The effect of the deviation of the wavefront corrector conjugation heights from their optimal values on the reduction of the achieved isoplanatism angle (relative to the maximum possible isoplanatism angle at the optimal conjugation height) was analyzed. Practical significance . The conjugation height values of the wavefront correctors obtained in this study can be used in the design and modernization of near-space observation systems.